Combined transoesophageal echo (TEE) and X-ray systems support interventional procedures. TEE utilizes an ultrasonic probe that is passed into a patient's oesophagus, and provides clear images because there is less signal attenuation with respect to transthoracial ultrasound imagery. This is particularly relevant for ultrasound imagery of the heart, because the heart is positioned close to the oesophagus. Currently in a combined TEE/X-ray system, the TEE probe is localized in the X-ray, with the TEE probe position and orientation determined from X-ray images. However the TEE probe cannot be tracked without the continuous acquisition of X-ray images or the use of additional tracking devices.
R. J. Housden et al., Ultrasound in Med. & Biol., Vol. 39, No. 6, pp. 993-1005, 2013, describe extended-field-of-view three-dimensional transesophageal echocardiography using image-based X-ray probe tracking.